Earlier in the day, anarchists who held a counter-demonstration clashed with police officers and far-right protesters in the seaside city.

Sunday's rally was dubbed "Macedonia for Macedonia".

Members of the Greek clergy and neo-fascist Golden Dawn party attended.

Ignoring a plea not to attend, members of the right-wing New Democracy party also turned up.

Long-standing name dispute

Sunday's rally was held in opposition to the use of the name "Macedonia" in any agreement struck between the two countries.

For many Greeks, Macedonia refers only to a province of northern Greece and accuse Skopje of having territorial designs over that region.

On the other hand, leaders in Skopje maintain they have a historical right to the name.

The country, which has an estimated two million citizens, was part of the Socialist Federal Republic of Yugoslavia until that country's breakup. Macedonia declared independence in 1991.

Greek opponents to the deal insist only calling the neighbouring country the Former Yugoslav Republic of Macedonia (FYROM), the name by which it joined the United Nations in 1993.

Right-wing and far-right parties have accused the Greek government, currently headed by the left-wing Syriza party, of betraying the country.

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Speaking to Greece's Skai television on Monday, New Democracy's vice president, Adonis Georgiadis, accused Prime Minister Alexis Tsipras of "start[ing] the story with the Macedonia [name talks] to create problems with [New Democracy]".

Tsipras has expressed flexibility in negotiations over the name dispute.

"It's totally groundless historically and absurd to seek the exclusivity of Macedonia," Tsipras said on Sunday, as reported by the Greek-language Ethnos newspaper.

"But it is not unreasonable to have the term 'Macedonia' included in a compound name, with either a geographical or a chronological qualifier, for all uses, to make absolutely clear that nobody claims other people's land or history."

The UN oversaw talks between the two countries last week, but a solution has yet to be reached.

Last week, a far-right group known as Crypteia - believed to be a breakaway from Golden Dawn - issued death threats to the Muslim Association of Greece and other civil society groups.

Earlier this month, the Athens-based activist group Keerfa announced that a spate of anti-immigrant attacks had seen more than 30 homes of Pakistani migrant labourers attacked in fewer than two weeks in Piraeus, a port city adjacent to the Greek capital.